Mechanical switchable automotive coolant pump

ABSTRACT

A coolant pump for providing a coolant to an engine includes a pump frame, a rotatable rotor shaft, a pulley wheel co-rotatably fixed to the rotor shaft, an axially shiftable ferromagnetic rotatable pump wheel, and an electromagnetic wet friction clutch arrangement. The pump wheel is axially shiftable with respect to the rotor shaft and the pump frame. The clutch arrangement comprises a static electromagnet, a clutch disk co-rotatably supported by the rotor shaft, a first clutch friction surface arranged at the clutch disk and a thereto corresponding second clutch friction surface arranged at the pump wheel, and a separate stop friction surface arranged at the pump wheel and a thereto corresponding static stop friction surface arranged at the static pump frame. The electromagnet, when fully energized, axially attracts the pump wheel so that the separate stop friction surface and the static stop friction surface engage to stop the pump wheel.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2015/069111, filed on Aug.20, 2015. The International Application was published in English on Feb.23, 2017 as WO 2017/028921 A1 under PCT Article 21(2).

FIELD

The present invention relates to a mechanical switchable automotivecoolant pump for providing a liquid coolant for an automotive engine.

BACKGROUND

A mechanical automotive coolant pump is mechanically driven by anautomotive internal combustion engine so that the coolant pump generallyrotates with a rotational speed which is proportional to the rotationalspeed of the engine. No coolant flow is needed in some situations, inparticular after starting a cold engine. A switchable automotive coolantpump is provided with a friction clutch so that the rotationalconnection between the pulley wheel of the pump and the pump wheel canbe engaged and disengaged as needed. The friction clutch can generallybe provided in a dry zone or in the wet zone of the pump. The disengagedclutch disk of a wet friction clutch still rotates and thereby rotatesthe coolant liquid which rotates the pump wheel. A significant dragmoment is in practice transferred by a wet friction clutch in thedisengaged clutch state so that a considerable pump performance isgenerated even if no pump performance is needed. The friction clutch canbe actuated by an electromagnet which attracts at least one clutchelement when the electromagnet is electrically energized.

SUMMARY

An aspect of the present invention is to provide a mechanical switchableautomotive coolant pump with a reduced pump performance when the wetclutch of the pump is disengaged.

In an embodiment, the present invention provides a mechanical switchableautomotive coolant pump for providing a liquid coolant for an automotiveengine. The mechanical switchable automotive coolant pump includes astatic pump frame, a rotor shaft configured to rotate, the rotor shaftbeing rotatably supported at the static pump frame, a pulley wheelconfigured to be co-rotatably fixed to the rotor shaft and to bemechanically driven by the automotive engine, a pump wheel comprising aferromagnet, and an electromagnetic wet friction clutch arrangement. Thepump wheel is configured to rotate and to be axially shiftable, and tobe rotatably supported and axially shiftable with respect to each of therotor shaft and the static pump frame. The electromagnetic wet frictionclutch arrangement comprises a static electromagnet configured to beenergized, a clutch disk which is co-rotatably supported by the rotorshaft, a first clutch friction surface arranged at the clutch disk, asecond clutch friction surface arranged at the pump wheel, a separatestop friction surface arranged at the pump wheel, and a static stopfriction surface arranged at the static pump frame. The first clutchfriction surface corresponds to the second clutch friction surface. Theseparate stop friction surface corresponds to the static stop frictionsurface. The static electromagnet, when fully energized, axiallyattracts the pump wheel so that the separate stop friction surface andthe static stop friction surface engage with each other, therebystopping the pump wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basisof embodiments and of the drawings in which:

FIG. 1 shows a longitudinal section of a mechanical switchableautomotive coolant pump in the with a clutch arrangement in the engagedstate;

FIG. 2 shows the enlarged clutch arrangement of FIG. 1;

FIG. 3 shows the clutch arrangement of FIG. 2 in a disengaged state; and

FIG. 4 shows the clutch arrangement of FIG. 2 in an intermediate state.

DETAILED DESCRIPTION

The mechanical switchable automotive coolant pump according to thepresent invention is provided with a static pump frame which is providedwith some kind of device to fix the coolant pump to an automotive engineor to an automotive frame. The pump frame can also be provided with apump wheel housing comprising a coolant inlet and a coolant outlet.

The coolant pump is provided with a rotatable rotor shaft which isrotatably supported at the pump frame. The rotor shaft is notnecessarily directly supported at the pump frame, but can be directlysupported at another rotatable part which is itself directly rotatablysupported at the static pump frame.

A pulley wheel is co-rotatably and axially fixed at the rotor shaft andis suitable to be mechanically driven by the engine. The pulley wheelcan generally be driven by any kind of mechanical transfer element suchas a gear wheel, a transmission belt, a friction wheel etc. The term“pulley wheel” as used herein is not limited to a belt-driven wheel. Thepulley wheel can, for example, be driven by the engine via atransmission belt. The pulley wheel is fixed to the rotor shaft and isnot rotatable nor axially shiftable with respect to the rotor shaft.

The coolant pump is provided with a rotatable and axially shiftable pumpwheel which is rotatably supported and which is axially shiftable withrespect to the rotor shaft and with respect to the pump frame. The pumpwheel can be axially moved and can rotate independently of the dynamicstate of the rotor shaft. The pump wheel is provided with a ferromagnetso that an energized electromagnet magnetically attracts and axiallypulls the ferromagnetic pump wheel.

The coolant pump is provided with an electromagnetic wet friction clutcharrangement of which the frictional clutch elements are arranged in thewet zone of the coolant pump. The clutch arrangement is provided with astatic electromagnet in the dry zone and with a clutch disc which isco-rotatably supported by the rotor shaft. The clutch disk alwaysrotates with the rotational speed of the rotor shaft.

The clutch disk is provided with a clutch friction surface, and the pumpwheel is provided with a corresponding clutch friction surface, both ofwhich are arranged in the wet zone. Both clutch friction surfaces are infull frictional contact with each other in the engaged clutch state sothat the pump wheel and the clutch disk rotate with the same rotationalspeed.

The pump wheel is provided with a separate stop friction surface, andthe pump frame is provided with a corresponding static stop frictionsurface. A sufficient braking torque is generated when the stop frictionsurfaces of the pump wheel and of the pump frame are in frictionalcontact with each other which completely stops the rotation of the pumpwheel when the wet friction clutch is in the fully disengaged state.

The friction clutch is in the engaged state if the electromagnet is notexcited so that the pump wheel rotates with the same rotational speed asthe rotor shaft. The stop friction surfaces are not in contact.

When the electromagnet is electrically excited, the pump wheel isaxially attracted by and in the direction of the electromagnet so thatthe stop friction surfaces of the pump frame and the pump wheel areaxially engaged with the result that the rotation of the pump wheel iscompletely stopped. The clutch friction surfaces are not in contact.

The coolant pump according to the present invention is provided with africtional brake arrangement defined by the stop friction surfaceswhich, in the disengaged state, completely stops any rotation of thepump wheel when the electromagnet is fully energized. A zero-flow of thecoolant is realized in the fully disengaged clutch state. The internalcombustion engine is therefore no longer cooled by a flowing coolant ifno cooling performance is needed or wanted.

In an embodiment of the present invention, the clutch disk can, forexample, be provided with a ferromagnet and be supported axiallyshiftable at the rotor shaft. The rotor shaft supports the pump wheeland the clutch disk. Since the clutch disk is provided with aferromagnet, the clutch disk is axially attracted by the energizedelectromagnet. Both the clutch disk and the pump wheel are axiallyattracted by the energized electromagnet. When the electromagnet isenergized, the clutch disk is axially pulled from an engaged position inwhich the clutch friction surfaces are in frictional engagement witheach other into a disengaged position in which the clutch frictionsurfaces are not in any frictional contact with each other. Since theclutch disk co-rotates with the rotor shaft, however, the rotatingclutch disk rotates the liquid coolant which thereby generates asignificant drag torque to the pump wheel. The energized electromagnetalso axially attracts the pump wheel so that the stop friction surfacescome into and remain in frictional contact with each other so that thepump wheel stops and no longer rotates.

In an embodiment of the present invention, the clutch disk can, forexample, be axially preloaded by a preload spring into an engaged clutchposition. If the electromagnet is not energized, the preload springpushes all elements of the clutch disk axially into the engaged clutchposition so that the clutch friction surfaces get in frictional contactwith each other with the consequence that the pump wheel co-rotates withthe rotor shaft. The pump wheel always co-rotates with the rotor shaftif the clutch actuation fails. The clutch arrangement is thereforefail-safe.

In an embodiment of the present invention, the pump wheel can, forexample, be provided with a non-ferromagnetic pump wheel body comprisingpump blades and with a separate ferromagnetic clutch ring which is fixedto the pump wheel body, for example, by bolts or by gluing. The pumpwheel body can be made of plastic which allows the realization of acomplex form with good fluidic properties and low weight, whereas theferromagnetic clutch ring can be provided with good electromagneticproperties and/or with good frictional properties.

In an embodiment of the present invention, the wheel-sided clutchfriction surface and the wheel-sided stop friction surface can, forexample, be provided at the ferromagnetic clutch ring. Bothpump-wheel-sided friction surfaces are provided at the ferromagneticclutch ring which is part of the pump wheel.

In an embodiment of the present invention, an axial stop surface can,for example, be provided to axially stop the clutch disk in thedisengaged position. The stop surface can, for example, be provided toco-rotate with the rotor shaft but to be axially fixed. Therotor-shaft-sided axial stop surface defines the axial disengagementposition of the clutch disk in the disengaged state, namely, when theelectromagnet is energized and thereby attracts the clutch disk into thedisengaged clutch disk position. The axial clutch disk stop limits theaxial movement path of the clutch disk so that the clutch disk is not infrictional contact with the pump wheel even if the pump wheel is alsoaxially attracted and pulled by the energized electromagnet into itsaxial disengagement position.

The clutch arrangement must not get jammed in the disengaged state. Thestop surface can, for example, lie in a transversal plane with respectto the longitudinal rotational axis of the rotor shaft and the pumpwheel. The stop surface does not generate any frictional force in anaxial direction so that the clutch arrangement always reliably returnsinto the preloaded engaged position if the electromagnet is notenergized.

In an embodiment of the present invention, the axial electromagnetic gapbetween the ferromagnetic clutch ring and the ferromagnetic clutch diskcan, in any clutch state, be at least two times larger than the axialelectromagnetic gap between the clutch ring and the electromagnet andbetween the clutch disk and the electromagnet. In other words, norelevant axial electromagnetic force is generated between theferromagnetic clutch ring and the ferromagnetic clutch disk. Relevantmagnetic forces in the axial direction are only directly generatedbetween the electromagnet and the ferromagnetic clutch ring, and betweenthe electromagnet and the ferromagnetic clutch disk. Another result ofthis arrangement is that no relevant eddy currents can appear betweenthe ferromagnetic clutch disk and the ferromagnetic clutch ring so thatno relevant electromagnetic drag torque exists.

In an embodiment of the present invention, the axial electromagnetic gapbetween the ferromagnetic clutch ring and the ferromagnetic clutch diskcan, for example, be at least 1.0 mm, for example, at least 2.0 mm.

In an embodiment of the present invention, the pump wheel can, forexample, be provided with a separate non-ferromagnetic friction ringarranged in the axial electromagnetic gap between the ferromagneticclutch ring and the ferromagnetic clutch disk. The friction ring has adouble-function, namely, providing good friction quality as theantagonist of the friction disc and also defining a sufficiently largeaxial electromagnetic gap between the ferromagnetic clutch ring and theferromagnetic clutch disk. The friction ring provides that the axialelectromagnetic gap between the ferromagnetic clutch ring and theferromagnetic clutch disk always remains above a minimum value even inthe engaged clutch state so that no relevant magnetic field and eddycurrents appear in this area.

In an embodiment of the present invention, an electronic clutch controlcan, for example, be provided to energize the electromagnet in afull-disengagement state. The clutch control is provided with anintermediate-engagement-state in which the clutch control provides theelectromagnet with less electric energy than in the full-disengagementstate. In the intermediate clutch-engagement-state, the electric energycan be on a level which puts the clutch wheel into a disengaged positionbut does not pull the pump wheel completely into its disengagementposition so that the stop friction surfaces of the pump wheel and thepump frame do not come into a full frictional contact. The pump wheelcan therefore still rotate and is rotated by the fluidic drag momentgenerated by the rotating clutch disk. With the third switching state ofthe clutch arrangement, a third rotational speed of the pump wheel canbe realized, namely, an immediate pump wheel speed which can, forexample, be in the range of 20% to 50% of the rotational speed of therotating clutch disk. The intermediate clutch state thereby allows thepump performance of the coolant pump to be more accurately adapted tothe cooling performance requirement.

An embodiment of the present invention is explained below underreference to the drawings.

The drawings show a mechanical switchable automotive coolant pump 10 forproviding a liquid coolant for an automotive engine 12. The coolant pump10 is mechanically driven by a rotating drive of the engine 12 whichdrives a transmission belt 13. The transmission belt 13 drives a pulleywheel 22 of the coolant pump 10. The coolant pump 10 of this embodimentis not provided with its own pump wheel housing, but is adapted to bemounted directly to an engine body 11 of the engine 12. The engine body11 defines an axial pump inlet channel 17 and an outlet volute 18 whichradially surrounds a pump wheel 60.

The coolant pump 10 is provided with a static pump frame 30 which isfixed to the engine body 11 by a suitable fixation element, namely byscrews and/or bolts. The pump frame 30 rotatably supports a rotatablerotor shaft 20 which is supported at the pump frame 30 by a shaftbearing 26, which is a roller bearing in the shown embodiment. The pumpframe 30 also supports a static electromagnet 32 which is provided as aring-shaped electromagnetic coil which, if energized with electricenergy, generates a toroidal electromagnetic field.

The pump frame 30 also fixedly supports a shaft sealing 34 whichsurrounds and seals the rotor shaft 20 and thereby fluidically separatesthe wet zone of the coolant pump 10 from the dry zone. The electromagnet32, the shaft bearing 26, the pulley wheel 22 and a part of the rotorshaft 20 are provided in the dry zone. The other rotating elements ofthe coolant pump 10 are provided and located in the wet zone.

The rotor shaft 20 co-rotatably supports a ferromagnetic clutch disk 51which is axially shiftable with respect to the rotor shaft 20 but whichco-rotates with the rotor shaft 20. The rotor shaft 20 is provided withan axial transmission groove 27, and the clutch disk 51 is provided witha corresponding transmission nose 52 protruding radially into the axialtransmission groove 27.

The rotor shaft 20 is also provided with a support structure 40 which isfixed to the rotor shaft 20 and which axially supports an axial preloadspring 28 which pushes the clutch disk 51 in axial distal direction awayfrom the support structure 40. The support structure 40 is provided withan axial stop surface 56 to axially stop the clutch disk 51 in thedisengaged position as is shown in FIG. 3.

The rotor shaft 20 rotatably supports a pump wheel 60 which is rotatableas well as axially shiftable with respect to the rotor shaft 20. Thepump wheel 60 is provided with a plastic pump wheel body 67 which is notferromagnetic, with a ferromagnetic clutch ring 66, and with a separatenon-ferromagnetic friction ring 70. The pump wheel body 67 is rotatablyand axially shiftably supported by a sliding bearing at the rotor shaft20. The sliding bearing is defined by a separate sliding bearing sleeve24 which is axially fixed by a fixation ring 23 at the rotor shaft 20.

The pump wheel body 67 comprises numerous pump blades 65 axiallyprotruding from the distal side of a pump wheel body base disk 74 of thepump wheel body 67. The ferromagnetic clutch ring 66 is fixed to thepump wheel body 67 at the proximal side of the pump wheel body base disk74 at the outer circumference thereof. The ferromagnetic clutch ring 66is provided with an axial clutch ring leg and with a radial clutch ringleg, as seen in cross-section. A stop friction surface 64 is provided atthe proximal end of the axial clutch ring leg which is in frictionalcontact with a corresponding stop friction surface 36 of the pump frame30 in the disengaged state of the friction clutch arrangement 50, as isshown in FIG. 3. Both clutch friction surfaces 62 and stop frictionsurface 64 lie in a transversal plane which is rectangular to therotational axis 21 of the rotor shaft 20.

The pump wheel 60 is also provided with a separate non-ferromagneticfriction ring 70 at the proximal surface of the radial clutch ring legof the ferromagnetic clutch ring 66. The proximal side of the frictionring 70 serves as a clutch friction surface 62 of the pump wheel 60. Theclutch disk 51 is provided with a ring-like clutch friction surface 54which corresponds with the clutch friction surface 62 at the pump wheel60. If the clutch friction surfaces 54, 62 are in full frictionalcontact with each other, the pump wheel 60 co-rotates with the clutchdisk 51 and the rotor shaft 20.

The electromagnet 32, the clutch disk 51, and the ferromagnetic clutchring 66 together define an electromagnetic wet friction clutcharrangement 50.

An electronic clutch control 14 is provided which controls and energizesthe electromagnet 32. In the engaged clutch state of the friction clutcharrangement 50, as is shown in FIGS. 1 and 2, the clutch control 14 doesnot energize the electromagnet 32 at all so that the axial preloadspring 28 axially pushes the clutch disk 51 into its engaged positionand so that the clutch friction surfaces 54, 62 are in full frictionalcontact with each other. The pump wheel 60 rotates with the rotationalspeed of the rotor shaft 20.

In the fully disengaged clutch state as is shown in FIG. 3, the clutchcontrol 14 fully energizes the electromagnet 32 so that the clutch disk51 is axially attracted with a relatively high axial attraction forceand the ferromagnetic clutch ring 66 of the pump wheel 60 is axiallyattracted with a relatively low axial attraction force. The clutch disk51 therefore first axially contacts the axial stop surface 56 and,thereafter, the stop friction surface 64 of the pump wheel 60 contactsthe corresponding stop friction surface 36 of the pump frame 30.

In the intermediate clutch state as is shown in FIG. 4, theelectromagnet 32 is moderately energized by the clutch control 14 sothat the clutch disk 51 is fully retracted into its disengaged position,but the pump wheel 60 is not substantially attracted. The stop frictionsurfaces 64, 36 therefore do not get into relevant frictional contact.As a result, the pump wheel 60 is rotated with about 20% of therotational speed of the clutch disk 51 because of the fluidic dragtorque transmitted by the liquid coolant which fills the wet zone.

In the engaged state of the clutch as is shown in FIGS. 1 and 2, theelectromagnetic gap E between the stop friction surfaces 64, 36 is about0.2 mm, and the electromagnetic gap F between the clutch disk 51 and theaxial stop surface 56 is about 0.4 mm. In the disengaged state of thefriction clutch arrangement 50 as shown in FIG. 3, the electromagneticgap D between the ferromagnetic clutch ring 66 and the wheel-sidedclutch friction surface 62 is about 1.5 mm. The axial thickness of theseparate non-ferromagnetic friction ring 70 is at least 1.0 mm, forexample, much more than 1.0 mm. The relatively large axialelectromagnetic gap D provides that no relevant axial magnetic forcesare present in this gap D and that relevant eddy currents do not appearin this area.

The present invention is not limited to embodiments described herein;reference should be had to the appended claims.

What is claimed is: 1-11. (canceled) 12: A mechanical switchableautomotive coolant pump for providing a liquid coolant for an automotiveengine, the mechanical switchable automotive coolant pump comprising: astatic pump frame; a rotor shaft configured to rotate, the rotor shaftbeing rotatably supported at the static pump frame; a pulley wheelconfigured to be co-rotatably fixed to the rotor shaft and to bemechanically driven by the automotive engine; a pump wheel comprising aferromagnet, the pump wheel being configured to rotate and to be axiallyshiftable, and to be rotatably supported and axially shiftable withrespect to each of the rotor shaft and the static pump frame; and anelectromagnetic wet friction clutch arrangement comprising, a staticelectromagnet configured to be energized, a clutch disk which isco-rotatably supported by the rotor shaft, a first clutch frictionsurface arranged at the clutch disk, a second clutch friction surfacearranged at the pump wheel, the first clutch friction surfacecorresponding to the second clutch friction surface, a separate stopfriction surface arranged at the pump wheel, and a static stop frictionsurface arranged at the static pump frame, the separate stop frictionsurface corresponding to the static stop friction surface, wherein, thestatic electromagnet, when fully energized, axially attracts the pumpwheel so that the separate stop friction surface and the static stopfriction surface engage with each other, thereby stopping the pumpwheel. 13: The mechanical switchable automotive coolant pump as recitedin claim 12, further comprising: a preload spring configured to axiallypreload the clutch disk into an engaged clutch position. 14: Themechanical switchable automotive coolant pump as recited in claim 12,wherein the clutch disk is ferromagnetic and is supported to be axiallyshiftable at the rotor shaft so that the clutch disk is axiallyattracted by the electromagnet when energized. 15: The mechanicalswitchable automotive coolant pump as recited in claim 14, wherein thepump wheel further comprises a non-ferromagnetic pump wheel body whichcomprises pump blades and with a separate ferromagnetic clutch ringwhich is fixed to the non-ferromagnetic pump wheel body. 16: Themechanical switchable automotive coolant pump as recited in claim 15,wherein the second clutch friction surface and the separate stopfriction surface are arranged at the separate ferromagnetic clutch ring.17: The mechanical switchable automotive coolant pump as recited inclaim 12, further comprising an axial stop surface configured to axiallystop the clutch disk in a disengaged clutch position. 18: The mechanicalswitchable automotive coolant pump as recited in claim 12, wherein theseparate stop friction surface and the static stop friction surface areconfigured to lie in a transversal plane. 19: The mechanical switchableautomotive coolant pump as recited in claim 15, further comprising: afirst electromagnetic gap between the separate ferromagnetic clutch ringand the clutch disk, a second electromagnetic gap between the separateferromagnetic clutch ring and the static electromagnet, and a thirdelectromagnetic gap between the clutch disk and the staticelectromagnet, wherein, the first electromagnetic gap is at least twotimes larger than the second electromagnetic gap and the thirdelectromagnetic gap. 20: The mechanical switchable automotive coolantpump as recited in claim 19, wherein the first electromagnetic gap is atleast 1.0 mm. 21: The mechanical switchable automotive coolant pump asrecited in claim 19, wherein the pump wheel further comprises a separatenon-ferromagnetic friction ring which is arranged in the firstelectromagnetic gap between the separate ferromagnetic clutch ring andthe clutch disk. 22: The mechanical switchable automotive coolant pumpas recited in claim 12, further comprising: an electronic clutchcontrol, wherein, the electronic clutch control is configured to fullyenergize the static electromagnet so as to obtain afull-engagement-state where the pump wheel is stopped, and theelectronic clutch control is configured to partially energize the staticelectromagnet so as to obtain an intermediate-engagement-state where thepump wheel is not completely stopped.